The present invention relates to a spherical sealing body used for exhaust pipe joints and a manufacturing method thereof.
Exhaust gas from an automobile engine is passed through an exhaust pipe disposed on a car body frame or the like from the engine and discharged into the atmosphere. However, the exhaust pipe is subjected to a repetitive bending stress due to the torque reaction force of the engine, force of inertia and so forth. Particularly in the case of a front wheel drive engine arranged transversely, the bending stress grows heavy as compared with that of an engine arranged longitudinally. Engine vibrations will therefore be brought into the car interior (along with noise) along an exhaust pipe suspension. Thus, not only noise is caused thereby but also a fatigue fracture may result in the exhaust pipe.
To solve such problem, a spherical pipe joint is disposed at a predetermined position along the exhaust pipe to absorb the stress.
A spherical sealing member has been used for conventional spherical pipe joints. It permits relative smooth angular motion between two of the exhaust pipes as the engine rotates relative to the automobile, prevents leakage of an exhaust gas from a pipe joint portion, and absorbs infinitesimal vibrations of the exhaust pipe arising as the automobile engine rotates.
As disclosed, for example, in Japanese Patent Publication (Kokoku) No. 58-21144, a wire mesh and a sheet-like refractory material (expanded graphite sheet, mica sheet or the like) are laminated with each other, wound cylindrically to obtain a preform body, and then the preform body which is compressed axially thereof has been used so far as the spherical sealing member.
The above-described sealing member consisting of a wire mesh and a refractory material has a structural integrity such that the refractory material is filled thoroughly in the wire mesh, thus both are entangled with each other. The refractory material exposed on a convex spherical surface of the sealing member is flexible and hence is easily conformed to the mating surface, therefore preventing leakage of an exhaust gas at the spherical joint. However, since the sealing member itself works as a rigid body to infinitesimal vibrations arising on the exhaust pipe, absorption of the vibrations can hardly be expected, thus leaving the problem of generation of noise due to the vibrations and sound in the car interior.